Dental cement and process of making the same



Patented Feb. 10, 1931 Patent? cit-t cs IQBGEN ERNST. TEQI LSEN, Q JEBLE- 1 L JYLN JERSEY DENTAL CEMENT AND PRQCES'SOE--M-AKI1TG THlife-Drawing This. application; is. a continuation in part of my;corpendingappl tion, Ser al: N 123 012, filed, in, the. United; StatesEatent Office on- 01: about July 16, L926, and, entitled 5 Improvementsin dentaL cements and; processesof making the Sa-m6- This. inventionrelates to, a new dental: cement. and the process of making the same.Ehere are twoiypes; of; cement generally em;

1 ployed: in dental? workone is these-called Zinc oxide cement and theother, is the socalled silicate cement.

Zinc oxide cements are preparedby admixingzim idew h-b smu hixide,.,niagnesi 1 oxide, etc. The s l catecemen cons s ofalumina,lime,silica and fiuorine, etc; Elnorine may or maynot be presentand is not essential.

lath pr ces fi man -factnr o zincnxid 2 ement it, is brought to, high te-npemture,

but not-suificientto se h ame; It s m rely concentrated. The productisthenground and passed'through. fine-sieves, cloth, etc, In the processof making the silicate cements,

the cement is brought to complete fusion and is then. po int m ld in imia to. glass. The resultingproduct; is; pulverized, sieved, molded, etc.

In order to. produce a plastic mass, from 3 these, which. can be worked;and which will harden, it is necessary to mix the powder containingbasic elements with-the proper proportion; of: phosphoric acid: Itisunnecessary togo into the various methods of preparing the phosphoricacid asga binder for these, cements, except to. state that the ac d -rre mixe w t celt aini mo ifie s,- z nc carbon te a en m-pleiandhs te too temperature to drive off the carbon dioxide.

lit-is then diluted with watertoltegulate the et ing ime; V

A amou t. f diflicu ta s experienced n t e use f; ental he nrpner P p' g5 he phq phatic ac d-l Q 1- i er lythefmi uiecf esic;elem nts qm on hmat-list in; .9 2 1 Rendertlie-cemsnt i to h use he enti W llteke asuitab e e-c n Q e P d o e cmbinewi hthe s i ne t h Application filedSeptember 20, 19218.v Serial No. 307,345;

hardened mass,willhavensatisfactory proper- 6P 7 ties n y t ch mounphospho c acid is used.i as is required to combine with: the bas onsttuents Pr s n Usuallyv an; excess of phosphoric acid is used, The free.acid remaini-n'g iiritates the puips of the teeth,cau sing-paiii, shockto the pulp a t enlo s Qf hcp lp- The objectof this invention istoeliminate this difliculty by accurately proportioning the amount ofacid requiredzto combine thoroughly with agivencement by incorporatingthe required" acidwith the dry powder in the proc s t manu a tur fth m nand preparing same for sale in such a nauner so that allthat isrequined' of; the user is to mix 3 water with the powder, apply thismixture to the tooth cavity, and thecement willsetin x ly the ame mann si dina y ment powder had been used with phosphoric acid, as a result ofwhich irritation and-pain or. harinto the tooth pulp are avoided to. agreat extent or entirely. The phosphoric acid in the present inventionis mixed at the manufacturing plant and is allowed to par tially combinewith the basic elements,- and this is, preferably done without the.exte-i na application of heat.

The strengtho-f the phosphoric acidused may be varied within certainlimits, and lw i ni sc sw lli s heprefe te lst cnst wi l som timesbe afictediby xisting dndiipns and ill lv hetewit r EQr. example. aq scQmnliisiglsst aefiflatl tn lE'z-Qjagn- 13? and. be sed advant ss s y with.ligatecement l -n 1 th, am an: id ementswh l hey m y be y f y -fo mypurpose with other zinc; oxide cements whei'e the lower limit of: I I0is 1 gHg0 to- IBEQE. Again, the temperature of calcination off thezincoxide in thepreparation thereof frequently affects the strength ofthe phosphoric acid which is to be preferred, as well as the range ofstrengths which may be used to advantage. Furthermore copper chloride oriodide, or silver salts, are sometimes added to the cements as agermicide, and such additions may affect the strengths of the phosphoricacid which is to be preferred, and it may even have an efi'ect on therange of useful strengths. Other conditions may have a like eflect. Itis therefore impossible to state exactly for all cements the beststrength of the phosphoric acid to be used therewith or the limitswithin which it maybe varied.

I can state, however, as a general rule that the ratio of H 0 to P 0should not be less than 2H O to 11 0 in the case of phosphoric acid usedwith silicate cements, and l fl H O to 11 0 for acid used with zincoxide cements; although as already stated this ratio should not be lessthan 2 to 1 even for some zinc oxide cements. Less than 1 I-I O to 1P Ois usually ineffective for dental cements, but this low limit of H 0 inthe acid is under certain conditions sometimes outside of theadvantageous limits. As stated above, various conditions will causevariations in the strengths of the phosphoric acid which it is best touse, as well as of the limits of strengths which may be used. Igenerally prefer to use acid of a strength of 3H O to 1P O that isorthophosphoric acid, H PO The composition of ordinary phosphoric acidof commerce is usually P O 4I-I O and it is necessary to addmetaphosphoric acid (1 0 -11 0) to bring the H 0 and P 0 into the properproportions. Although the proportion P O 3I-I O is preferred, it mayvary between, say, P O 3 H O and P 0 QH O, or even P O 1 H O as abovestated. Too much water is to be avoided, sinceitwould cause prematurehardening of the cement.

The following are examples of some silicate cements:

1 II Na SiF 142 142 Cali 2O 20 Al O .xH O 158 158 SiO 102 114 parts ofthe cement to50 parts of phosphoric acid.

Zinc oxide cements, for example, cements comprising parts of zinc oxideand 10 parts of magnesium oxide or corresponding quantities of magnesiumcarbonate or/and silicofluoride would require relatively more phosphoricacid, due to greater basicity. A suitable mixture could be formed from150 parts of zinc oxide cement and parts of phosphoric acid, but theamount of phos phoric acid may be varied between 100 and 150 parts.

The powder and the phosphoric acid are mixed together at roomtemperature, the reaction between them generating suflicient heat, underordinary working conditions to heat the mass to about between about 100and 180 F. or about 30 to 70 C., which is sufficient to cause removal ofthe excess water present; and allowing the mass to stand until cool willenerally result in a dry mass which is then to be comminuted orpowdered.

Apparently the phosphoric acid is present therein in some combined formand this seems to become cementitiously active on the addition of water.While this seems to be the case, yet I do not intend to restrict myinvention'to any theory; but aside from any theory, the dry powder whenmixed with water as above described becomes cementitious and sets.

The resulting powder is packaged for sale. It is ready for use and it isnecessary only to add the desired amount of water to produce a desirableplastic mass ready for use and which upon standing will readily harden.The thinner it is desired to make this cement, for example cementing forcrown and bridge work to teeth,the more water will be added. Less waterwill be added when a thick plastic mass is desired, as for fillingteeth.

The specific proportions given above are merely illustrative and thisinvention is of broad application to all dental cements of the characterabove described. The composition both in respect to constituents andproportions may be widely varied.

Having described my invention, what I now claim is:

1. The herein-described composition of matter in dry powder formsuitable for use as a dental cement by the addition thereto of wateralone, said composition consisting of approximately parts by weight of asilicate cement and from 40 to 60 parts by weight of pureorthophosphoric acid or the equivalent of said acid in P 0 radical, saidingredients being mixed'together at a temperature sufficiently low toretain the mixture in an unstable condition capable of subsequently reacting with the added water to form aplastic mass capable of hardening.p

2. The herein-described composition of matter in dry powder formsuitable for use as a dental cement by the addition thereto of wateralone, said composition consisting of approximately partsby weight of abasic metaloxide cement and from 100" to 150 parts by weight of aphosphoric acid containing the P radical in combination with from 1 to 2molecules of combined Water, said ingredients being mixed together at a5 temperature sufficiently low to retain the mixture in an unstablecondition capable of subsequently reacting with the added Water to forma plastic mass capable of hardening.

J ORGEN ERNST THOMSEN.

